PRWeek has learned that key figures in Number 10, and a number of ministerial special advisers, are becoming increasingly restless about the comms set-up in certain departments.

Last week's fiasco over free school milk is the latest negative headline to enrage coalition comms chiefs such as Andy Coulson, Gabby Bertin and Jonny Oates.

Two weeks earlier, Downing Street was forced to intervene after Justice Minister Crispin Blunt suggested prisoners could be allowed to hold parties. Number 10 insisted there would be 'no such parties' after the comments were reported in a newspaper.

And in July, education secretary Michael Gove was forced to apologise to the Commons and council leaders after it emerged that an initial list of 715 Building Schools for the Future projects was riddled with errors.

Coalition comms chiefs are also said to be alarmed by the number of sensitive documents that have been leaked to the press in recent weeks, with many pointing the finger at Whitehall departments. And there is concern that some departmental press offices have distributed quotes that are overtly political. For example, earlier this year, a Department for Education spokesman was widely quoted accusing Labour's Ed Balls of 'confecting lies' about school selection.

A source close to Downing Street said: 'Number 10 and some of the new spads [special advisers] are increasingly frustrated with the standard of comms. They're annoyed at recent cock-ups. They're especially annoyed with the Department for Education.

'There is a recognition in Downing Street that something has to be done. They now realise that their hands-off approach was a touch naive.'

Senior Whitehall figures responded by privately attacking Downing Street for seeking to 'shift the blame' from hapless ministers. Another Whitehall source said Number 10 was 'too laissez faire in the early days'.